Configure MPLS over GRE Tunnels

MPLS LSPs can use GRE tunnels to cross routing areas, Autonomous Systems, and ISPs. Bridging MPLS LSPs over an intervening IP domain is possible without disrupting the outlying MPLS domain.

LSPs can reach any destination that the GRE tunnels can reach. MPLS applications can be deployed without requiring all transit nodes to support MPLS, or requiring all transit nodes to support the same label distribution protocols (LDP or RSVP). If you use CSPF, you must configure OSPF or IS-IS through the GRE tunnel. Traffic engineering is not supported over GRE tunnels; for example, you cannot reserve bandwidth or set priority or preemption.

For more information about GRE tunnels, see the JUNOS Internet Software Configuration Guide: Interfaces and Class of Service.